Linking forests changes to CO2 rise and climatic changes

Studies on ≥1 hectare permanent plots in the Amazon indicate accelerating forest dynamics and increasing biomass in old-growth forests over the last 30 years. Similar results have been found in forest plots in Africa and, to a lesser degree, in Asia, providing evidence that increasing carbon storage in old-growth forests might be a pan-tropical phenomenon.

Project description

Several explanations have been put forward to explain these observed changes, including the effects of increased atmospheric CO2 concentration due to the burning of fossil fuels, the effects of changing climate, recovery from past disturbances and the effects of increased nutrient depositions.

The stable isotope record in the cellulose of tree rings could provide more insight in the factors causing long-term changes in tropical forests. One of the main objectives of my PhD research is to reconstruct the (local) climatic conditions for the last 150-200 years in TroFoClim fieldwork areas. A special focus will be on the frequency of droughts. Trying to reconstruct climatic conditions is challenging and I am therefore using three different tree ring parameters: ring width and carbon and oxygen isotopes. All are, in different ways and degrees, influenced by climate. The second main topic of my PhD research is to find indications for the so called ‘CO2 fertilization effect’ by using carbon isotopes as a proxy for internal [CO2] in the leaves (ci). Very simplistic; if increasing atmospheric CO2 concentration allows plants to absorbed CO2 with less water loss, we expect them to be able to maintain higher ci levels. If water is a limiting factor (during some parts of the day or of the year), a lower water loss might allow plants to extent their growth into the dry season or during the drier parts of the day, hence explaining increased growth rates.

My PhD research is part of a pan-tropical study on the long-term changes of growth and dynamics in tropical forests and the potential factors causing them (the TROFOCLIM project). I am working at the Bolivian fieldwork site;  the 100.000 ha FSC forest concession of La Chonta. My final data set will, however, also include trees from Thailand and Cameroon (see PhD projects of Mart Vlam and Peter Groenendijk).

MSc theses